Conditional Structures in Shell Scripting - II

Nested if..else
Nested if else statements can be useful to check multiple conditions. For example, given a number first check whether it is positive or negative then  test the range in the respective domains.
Syntax:
                       if condition
           then
               if condition
               then
                  statement1
               else
                  statement2
               fi
                  else
               statement3
               fi

Example :

	read x
	if [ $x -ge 0 ]
	then
	if [ $x -ge 10 -a $x -le 100 ]
	then
	echo "$x is between 10 and 100"
	else
	echo "$x is between 0 and 9"
	fi
	else
	if [ $x -le -10 -a $x -ge -100 ]
	then
	echo "$x is between -10 and -100"
	else
	echo "$x is between -1 and -9"
	fi
	fi

view raw nested.sh hosted with ❤ by GitHub

if..elif statements

Syntax
                if condition1
       then 
            statement1
       elif condition2
       then   
            statement2
       elfi condition3
       then 
            statement3
       else
            #if none of the conditions are satisfied
            statement4 
       fi

	echo "Enter your favourite tech company"
	read x
	if [ -z $x ]
	then
	echo "You have entered a NULL string."
	elif [ $x = "Apple" ]
	then
	echo "I guess you might be liking iphone and ipad "
	elif [ $x = "Google" ]
	then
	echo "I guess you might be liking Android and Chrome"
	elif [ $x = "Microsoft" ]
	then
	echo "I guess you might be liking Windows and Office"
	elif [ $x = "Nokia" ]
	then
	echo "Sorry who Nokia?"
	else
	echo "Sorry search failed :( "
	fi

view raw ifelif.sh hosted with ❤ by GitHub